We have accrued new data that suggests a new nutritional basis as a contributory pathway to the development of atherosclerotic heart disease. The overall pathway involves an interplay between dietary intake of lipid (the choline moiety of phosphatidyl choline), intestinal microbiota (gut flora), genetic susceptibility (hepatic expression levels of flavin monooxygenase 3, FMO3), and generation of pro-atherosclerotic metabolites that promote atherosclerotic heart disease and its major adverse complications (myocardial infarction (MI), stroke, and death). Intestinal microbiota (gut flora), comprised of trillions of typically non-pathogenic commensal organisms, serve as a filter for our greatest environmental exposure - what we eat. Gut flora play an essential role, aiding in the digestion and absorption of many nutrients. Alterations in gut flora can be associated with changes across a wide range of metabolic pathways. Similarly, alterations in diet influence both the composition of gut flora and plasma levels of metabolites. Animal studies have recently shown that intestinal microbial communities can influence traits, and metabolomic studies of inbred mouse strains have shown that gut microbiota may play an active role in the development of complex dysmetabolic phenotypes, such as susceptibility to insulin resistance and non-alcoholic fatty liver disease. Demonstration of a link between gut flora dependent phospholipid metabolism and atherosclerosis risk through generation of pro-atherosclerotic metabolites has not yet been reported. The overall goal of this proposal is to test the hypothesis that gut flora dependent metabolism of dietary phosphatidylcholine is mechanistically linked to the pathogenesis of cardiovascular disease. The specific aims are: Aim 1) Testing the hypothesis that dietary phosphatidylcholine metabolites choline, TMANO and betaine are both diagnostic markers for cardiac risk and mechanistically linked to development of atherosclerosis. Aim 2) Testing the hypothesis that gut flora plays a modulatory role in atherosclerosis.